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Subel. A
6 questions
Subelement A

RADAR Principles

Section 4

Power, Pulse Width, PRR

A pulse RADAR has a pulse repetition frequency (PRF) of 400 Hz, a pulse width of 1 microsecond, and a peak power of 100 kilowatts. The average power of the RADAR transmitter is:

  • 25 watts.
  • Correct Answer
    40 watts.
  • 250 watts.
  • 400 watts.

Duty Cycle = Pulse Width / PRF

Given: Pulse Width = 1 microsecond = 1 * 10^(-6) seconds PRF (Pulse Repetition Frequency) = 400 Hz

Duty Cycle = 1 * 10^(-6) seconds / 400 Hz Duty Cycle = 0.0000025

Now, to calculate the average power:

Average Power = Peak Power * Duty Cycle Average Power = 100,000 watts * 0.0000025 Average Power = 40 watts

So, the correct answer is that the average power of the RADAR transmitter is 40 watts.

Mnemonic: "DutyCyclePower"

Last edited by kacela. Register to edit

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A shipboard RADAR transmitter has a pulse repetition frequency (PRF) of 1,000 Hz, a pulse width of 0.5 microseconds, peak power of 150 KW, and a minimum range of 75 meters. Its duty cycle is:

  • 0.5
  • 0.05
  • 0.005
  • Correct Answer
    0.0005

Duty Cycle = (PRF)x(PW)

Duty Cycle = (1000 Hz)x(0.0000005 sec)

Duty Cycle = 0.0005

Last edited by wrkelsik. Register to edit

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A pulse RADAR transmits a 0.5 microsecond RF pulse with a peak power of 100 kilowatts every 1600 microseconds. This RADAR has:

  • Correct Answer
    An average power of 31.25 watts.
  • A PRF of 3,200.
  • A maximum range of 480 kilometers.
  • A duty cycle of 3.125 percent.

Duty Cycle = 0.5 μs / 1600 μs

Duty Cycle = 0.0003125

Pavg = (Duty Cycle) x (Ppeak)

Pavg = 0.0003125 x 100,000 kW

Pavg = 31.25 W

Last edited by wrkelsik. Register to edit

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If a RADAR transmitter has a pulse repetition frequency (PRF) of 900 Hz, a pulse width of 0.5 microseconds and a peak power of 15 kilowatts, what is its average power output?

  • 15 kilowatts.
  • 13.5 watts.
  • Correct Answer
    6.75 watts.
  • 166.67 watts.

Duty Cycle = (PRF)x(PW)

Duty Cycle = (900 Hz)x(0.0000005 sec)

Duty Cycle = 0.00045

Pavg = (Duty Cycle) x (Ppeak)

Pavg = 0.00045 x 15,000 kW

Pavg = 6.75 W

Last edited by wrkelsik. Register to edit

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What is the average power if the RADAR set has a PRF of 1000 Hz, a pulse width of 1 microsecond, and a peak power rating of 100 kilowatts?

  • 10 watts.
  • Correct Answer
    100 watts.
  • 1,000 watts.
  • None of these.

Duty Cycle = (PRF)x(PW)

Duty Cycle = (1000 Hz)x(0.000001 sec)

Duty Cycle = 0.001

Pavg = (Duty Cycle) x (Ppeak)

Pavg = 0.001 x 100,000 kW

Pavg = 100 W

Last edited by wrkelsik. Register to edit

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A search RADAR has a pulse width of 1.0 microsecond, a pulse repetition frequency (PRF) of 900 Hz, and an average power of 18 watts. The unit's peak power is:

  • 200 kilowatts.
  • 180 kilowatts.
  • Correct Answer
    20 kilowatts.
  • 2 kilowatts.

Duty Cycle = (PRF)x(PW)

Duty Cycle = (900 Hz)x(0.000001 sec)

Duty Cycle = 0.0009

Pavg = (Duty Cycle) x (Ppeak)

Ppeak = (Pavg) / (Duty Cycle)

Ppeak = 18 W / 0.0009

Ppeak = 20,000 W or 20 kW

Last edited by wrkelsik. Register to edit

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